Steel SKH57
JIS SKH57
SKH57 is the JIS high-cobalt molybdenum-tungsten high-speed steel corresponding to AISI M42, combining cobalt with vanadium carbides for hot hardness above standard HSS grades.
Reference datasheet — SKH57 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ANN condition
SKH57 tempers and conditions
SKH57 is supplied in 6 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hardened & tempered to 62–64 HRC | Higher tempering temperature / slightly lower austenitizing for interrupted cuts, broaches and larger cross-sections needing toughness. | 63 HRC | — | |||
Hardened & tempered to 64–66 HRC | Usual cutting-tool condition: 1180–1200 °C quench + 3 × 550 °C temper, best balance of wear resistance and toughness. | 65 HRC | — | |||
Hardened & tempered to 66–68 HRC | Peak secondary-hardening condition for taps, drills and form tools on hardened or abrasive workpieces where wear, not shock, governs. | 67 HRC | — | |||
ANNDefault Annealed | Standard mill-supplied soft condition for machining tool blanks before hardening. | 540 | 880 | 10 | 26 HRC | — |
Hardened & tempered + steam oxide (blue/black finish) | Choose for taps and drills where the Fe3O4 layer holds lubricant and reduces galling on gummy materials. | 2,150 | 2,600 | 1 | 65 HRC | 2.7 % IACS |
Hardened & tempered + PVD coating | Standard for production cutting tools: coating raises surface hardness and hot-oxidation resistance while the substrate stays at 65–67 HRC. | 2,200 | 2,650 | 1 | 66 HRC | 2.7 % IACS |
What is SKH57?
SKH57 is the JIS high-cobalt molybdenum-tungsten high-speed steel corresponding to AISI M42, combining cobalt with vanadium carbides for hot hardness above standard HSS grades. It is used for cutting tools working hard or tough materials, supplied annealed (265 HB, 26 HRC, 880 MPa tensile, 540 MPa yield, 10 % elongation) or hardened 62-68 HRC with steam-oxide and PVD finishes. Listed maximum service temperature is 400 C and machinability about 25. Toughness and grindability are lower than M2-type steels and cost is higher, so SKH51/M2 or a PM-HSS grade is the alternative when edge chipping or tool cost dominates. SKH57 has a density of 8.3 g/cm³ (0.3 lb/in³), heavier than 99% of steel grades. It melts at 1,260°C (2,300 °F). SKH57 has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 70% of steel grades. Elongation at break is 10% and the elastic modulus is 225 GPa (32.6 Msi).
What is SKH57 used for?
- Hobs
- Broaches
- High-speed cutting tools
Limitations
- Low fracture toughness — 22 MPa·√m (20 ksi·√in), worse than 98% of steel grades
- Poor heat conductor — 19 W/m·K (11 BTU/hr·ft·°F), worse than 97% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- High embodied carbon — 4.5 kg CO₂/kg, worse than 95% of steel grades
SKH57 properties
Typical room-temperature values for SKH57-ANN; bars are the position among steel grades.
Physical3
SKH57 has a density of 8.3 g/cm³ (0.3 lb/in³), heavier than 99% of steel grades. It melts at 1,260°C (2,300 °F).
Mechanical12
SKH57 has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 70% of steel grades. Elongation at break is 10% and the elastic modulus is 225 GPa (32.6 Msi).
Thermal6
SKH57 is rated for continuous service to 400°C (752 °F). It conducts heat at 19 W/m·K (11 BTU/hr·ft·°F), worse than 97% of steel grades. Thermal expansion is 10.2 µm/m·K (5.67 µin/in·°F).
Electrical3
SKH57 conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of SKH57 takes about 60 MJ of energy and emits 4.5 kg of CO₂ — more than 96% of steel grades. Typical recycled content is 35%.
Manufacturability8
SKH57's machinability is poor (25/100, worse than 93% of steel grades); weldability not recommended (12/100); formability not recommended (8/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. SKH57 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SKH57
Is SKH57 easy to machine?
Machine only in the annealed state with sharp cobalt-HSS or coated carbide, low speed and rigid setup; after hardening use grinding (CBN or friable SG wheels), EDM or hard turning with CBN — MC vanadium carbides make grindability poor.
Can SKH57 be welded?
Not a structural weld grade; repair only by TIG/micro-plasma with matching HSS filler, 500–550 °C preheat and immediate re-temper to avoid quench cracks.
Can SKH57 be formed, bent or molded?
Hot work only: forge 1100–1150 °C, stop above 950 °C, cool slowly then spheroidize anneal at 850–900 °C; no cold forming. Harden 1180–1210 °C in vacuum/salt, quench in gas or oil, then temper 3 × 1 h at 540–560 °C.
SKH57 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CJIS G4403 | 1.2 – 1.45 | 1.3 |
| Si | ≤ 0.45 | 0.3 |
| Mn | ≤ 0.4 | 0.3 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Cr | 3.5 – 4.5 | 4 |
| Mo | 3 – 4 | 3.5 |
| W | 9 – 11 | 10 |
| V | 3 – 3.5 | 3.3 |
| Cogives red hardness | 9 – 11 | 10 |
| Niresidual | ≤ 0.25 | |
| Curesidual | ≤ 0.25 | |
| Fe | balance |
What surface finishes work on SKH57?
Cannot be anodized; use steam oxide, black oxide, nitrocarburizing (thin case only) or PVD TiN/TiAlN/AlCrN — keep PVD deposition below the tempering temperature to preserve 65+ HRC.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel SKH57 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- M42
How much does SKH57 cost?
SKH57 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SKH57 — frequently asked
What is SKH57 used for?
SKH57 is typically used for hobs, broaches and high-speed cutting tools. In short: highest red hardness HSS; high-cobalt M42 type; grinds slower than M2.
What is the yield strength of SKH57?
SKH57 has a typical yield strength of 540 MPa (78.3 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 70% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is SKH57 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Machine only in the annealed state with sharp cobalt-HSS or coated carbide, low speed and rigid setup; after hardening use grinding (CBN or friable SG wheels), EDM or hard turning with CBN — MC vanadium carbides make grindability poor.
Can SKH57 be welded?
Not readily — weldability is rated not recommended (12/100). Not a structural weld grade; repair only by TIG/micro-plasma with matching HSS filler, 500–550 °C preheat and immediate re-temper to avoid quench cracks.
What surface finishes work on SKH57?
Cannot be anodized; use steam oxide, black oxide, nitrocarburizing (thin case only) or PVD TiN/TiAlN/AlCrN — keep PVD deposition below the tempering temperature to preserve 65+ HRC.
Can SKH57 be formed, bent or molded?
Hot work only: forge 1100–1150 °C, stop above 950 °C, cool slowly then spheroidize anneal at 850–900 °C; no cold forming. Harden 1180–1210 °C in vacuum/salt, quench in gas or oil, then temper 3 × 1 h at 540–560 °C.
What is the maximum service temperature of SKH57?
SKH57 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SKH57-ANN and SKH57 QT-PVD?
ANN is the default condition — standard mill-supplied soft condition for machining tool blanks before hardening. QT-PVD: standard for production cutting tools: coating raises surface hardness and hot-oxidation resistance while the substrate stays at 65–67 HRC. Yield strength is 540 MPa in ANN versus 2,200 MPa in QT-PVD.
How much does SKH57 cost?
SKH57 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- JIS G4403 High-speed tool steel materials — JSA (2015)
- ASTM A600 Standard Specification for Tool Steel High Speed — ASTM (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (Tool Steels) — ASM International (1990)
- ASM Specialty Handbook: Tool Materials — ASM International (1995)
- Cobalt high-speed steel (SKH57/M42-class) bar datasheets — Hitachi Metals / Proterial, Nachi-Fujikoshi, Böhler (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.